1. Technical Field of the Invention
The present invention relates to a filament assembly including primary coils disposed in a spiral around an axis of revolution and secondary coils connected to the primary coils by a spacer.
2. Description of the Prior Art
One known filament assembly in the art includes a filament composed of several portions disposed in two planes. Two metal rods, electrically connected to two of the filament portions and to an external electrical circuit, enable the filament assembly to be supplied with current. These two metal rods have at one end a hook oriented about an axis of revolution and are electrically connected to the two portions by two spacers which are inserted in the hooks on the metal rods. Each spacer is thus in contact with the hook of a metal supply rod at an attachment point dependent on a curvature of the spacer.
Such a spacer is obtained while the filament is being manufactured by a momentary interruption of a coiling process for making the turns of the filament. This interruption in the coiling process is a tricky operation that results in a random curvature of the spacer, that is to say the attachment point may be situated either to the left or to the right of the axis of revolution of the hook on the metal rod. However, the applicant has found that, during an operation of assembling the filament and the metal current supply rods, inserting the spacer in the hook of a metal rod is particularly difficult if the attachment point is situated on a certain side of the axis of revolution of the hook, and easier if the attachment point is situated on the other side. Essentially the degree of difficulty of inserting the spacer in the hook is dependent upon an orientation of the hook.
However, in various commercially available lamps, the two metal supply rods are symmetrical. Consequently, when the attachment point of a spacer is situated on one side of the axis of revolution of the hook to which it is connected and the attachment point of the other spacer is situated on the other side of the axis of revolution of the hook to which it is connected, assembling the filament is difficult.
However, even if the two supply rods are asymmetrical, a similar problem arises when the two attachment points are situated on the same side of the two axes of revolution of the hooks on the metal supply rods.
Such a situation gives rise to a relatively long assembly time and to risks of breakage of the filament.